ufs kernel parameters with unbuffered file systems

From: Rick Denoire (100.17706_at_germanynet.de)
Date: 11/05/03 

Date: Wed, 05 Nov 2003 00:03:37 +0100

Hello

In Solaris 2.7, the default value of ufs_WRITE is 1, meaning that when
an ufs_HW amount of data has been collected for an I/O operation, the
input stream into the buffer will be stopped, until the buffer holding
the data to be transfered goes down to ufs_LW and is empty enough to
accept more data.

I have set ufs_LW to 8MB and ufs_HW to 16MB in /etc/system and am
waiting for a chance to reboot (for 3 months now). But since the file
system I am concerned about is mounted with the option forcedirectio
(for Oracle work), I am wondering if the settings mentioned will have
any effect. forcedirectio switches buffering of filesystems entirely
off.

My goal is to overcome any potential throttle introduced by Sun in
ancient times, where peripheric devices were slow and memory
expensive. This host (E3500, 4 CPUs, 2GByte RAM) is equipped with two
FibreChannel connections 2GBit/s each. I already set the maxphys
kernel parameter to 1 MB. Anything else required?

Thanks in advance
Rick Denoire